//
// Created by wze-zero on 2024/8/24 024.
//
#include <iostream>
#include <iomanip>

#define PI 3.14

using namespace std;

int main() {
    double r, area;
    cin >> r;
    area = PI * r * r;
    cout << fixed << setprecision(2) << area << endl;
    return 0;
}